JPS60179364A - Hydraulic brake system - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a hydraulic brake system, and particularly to a hydraulic brake system suitable for automobiles.

[Technical background of the invention and its problems] This type of hydraulic brake system has a dual brake circuit connected to the front and rear wheel brakes, respectively,
A pedal-operated brake pressure generator consisting of a brake booster and a mask cylinder, connected to an auxiliary energy source, a brake pressure regulator arranged in a pressure passage leading to the rear wheel brake, and a rear wheel brake. The boost effect is reduced by reducing the pressure fluid path leading from the brake to the pressure fluid reservoir and the isolating valve adapted to be switched to the open position and the auxiliary energy transmitted to the brake pressure generator. A switching valve, a sensor that determines and evaluates the rotational state of the wheels, controls the brake pressure distribution between the front wheels and the rear wheels, and influences changes in the brake pressure when the wheels tend to lock up, and an electric circuit mechanism. Configured with the necessary features.

Many brake systems with slip control are known. In such a brake system,
For example, a sensor consisting of an inductive transducer measures the rotational state of a wheel directly or indirectly, and when a wheel lock state is about to occur due to the test value or time change, a sensor consisting of an inductive transducer measures the wheel's brake pressure change. Its influence is exerted. In order to control the brake slip of a wheel to a value that is favorable for deceleration, running stability and maneuverability of the vehicle, the wheel or the wheels that are controlled together according to a predetermined relationship by using a regulator consisting of a control valve or the like. By reducing the group brake pressure, keeping it constant or, if necessary, increasing it again, the tendency for the wheels to lock is counteracted.

During braking, the adhesion of the wheels to the road surface as well as the braking force of the wheels depend on various parameters, and the most important of these parameters vary within a very wide range, which is why such brake slip control devices are required. will be expensive. Therefore, in improving brake slip control devices, it is important to simplify their structure and manufacture so that there is no or only insignificant loss in slip control accuracy. The purpose of

Hydraulic brake systems that incorporate an auxiliary energy source are
West German published patent application nos. 3040561 and 304056
It has already been disclosed in No. 2.

In this brake system, the brake pressure generator includes a brake pressure control valve, which is controlled by a brake pedal. The brake pressure control valve is also equipped with one or two mask cylinders of the single or tandem type that are integrated with the brake pressure control valve and actuated by the brake pedal force augmented by auxiliary energy. Brake circuit is connected.

For the purpose of brake slip control, a solenoid switching valve inserted in the brake circuit is actuated. This electromagnetic switching valve can cut off the supply of hydraulic medium to the wheel brakes, thereby preventing a further increase in brake pressure. The brake pressure is
By opening the outlet towards the reservoir for pressure medium supply, the pressure is reduced to the desired pressure level. Furthermore, the solenoid switching valve supplies dynamic pressure to the working chamber of the mask cylinder from an auxiliary energy source, so that the delivery of the pressure medium in the reservoir is compensated and the discharge of the working chamber due to repeated depressurization is prevented. thwarted. Such braking systems necessarily lead to high consumption of hydraulic means.

In addition, brake systems with open-center mask cylinders are already known (German Published Patent Applications No. 3040548 and No. 3040540). In this braking system, a throttle valve is provided in the pressure medium line of the pump supplying the auxiliary pressure, and this throttle valve is not closed until the brake is applied. Therefore, the pressure built up by the auxiliary energy source is transmitted and an increase in braking force can be ensured. Apart from this, the configuration of the hydraulic unit consisting of the brake valve and mask cylinder, which are operated when a control action is performed, and the configuration of the electromagnetic valve are the same as those described in 1. This is similar to the brake system used in the previous model.

The problems that arise in the configuration of the brake system are:
It concerns the application of brake force distribution to static and dynamic loads on the axle. Normal brake force distributors have uniform pressure response control. Various types of load-responsive or deceleration-responsive brake force control units are known. All these brake force control units are only relatively loosely adapted to the actual axle load distribution.

Furthermore, brake force distributors are already known, in which when the vehicle is stationary, the load distribution of its static shaft is detected by a sensor, and the signal from the sensor is transmitted to the computer. This microcomputer takes these detected values and the measured values of brake pressure into account and uses the recorded mathematical relationships (European Patent Application No. 6224
Adjust the brake force distribution to the front and rear axles based on No. 6). Furthermore, such brake boosters do not measure the actual friction value produced during braking, but rather the calculated 11i! A disadvantage is that the friction value is determined for the distribution of the braking force. Therefore, in order to reliably avoid dangerous overbraking of the rear axle, in many cases
During braking, the braking system is required to reduce the effects produced on the rear axle to be less than physically possible. Furthermore, it must be taken into account that the actual friction values often differ significantly from the calculated and predetermined nominal values.

When setting the brake force distribution with respect to the recorded mathematical relationship, the brake characteristic value, which is a constant value, is likely to change greatly due to manufacturing tolerances, temperature changes, wear, etc. For this reason, brake slip on the front and rear axles is controlled by wheel and body sensors as well as logic circuits.
'= and it has already been proposed to control the brake slip on the rear axle according to the brake slip on the front axle so that the coefficient of friction on the rear and front wheels is approximately equal for each brake application. .

However, such brake force distributors still have the disadvantage that in most cases of overbraking, the front wheels lock first and the rear wheels only follow if high brake pressure is present. Remaining. This is because locking the rear wheels can lead to skidding, which is very dangerous, while the loss of maneuverability due to locking the wheels is still not as bad as skidding.
It's important. If the brake pedal is depressed even further, what already happens on slippery roads as a result of relatively small brake pedal pressures, a locking of the front and rear wheels and a consequent lack of maneuverability and driving stability can occur. There is no brake booster that can prevent both.

Therefore, braking systems have already been proposed that control the distribution of braking force to the front axle and the rear axle and prevent the wheels from locking whenever the brakes are applied. For this purpose, hydraulic units and brake pressure regulators are used to control the brake force distribution and also for brake slip control, which makes the overall manufacturing effort of the brake system relatively low. can. Although the brake system described above is characterized as particularly simple, it is nevertheless able to optimally distribute the braking force to the front and rear wheels for each brake application. As a result,
By making the adhesion of the front and rear axles uniform and preventing the wheels from locking, the running stability and maneuverability of the vehicle can be maintained even during an emergency stop on an icy road.

However, when reducing the brake pressure at the front axle, the brake pressure generator consists of an open center brake booster combined with a mask cylinder, and a throttle valve directly connected to one of the two brake circuits. In this brake system, the brake pressure changes in the front wheel brakes cannot be made completely uniform. The reason for this is that when inactive, ie when the auxiliary energy source is short-circuited, the brake pedal force continues to act on the mask cylinder circuit rather than on the brake circuit connected to the throttle valve. As a result, a predetermined residual pressure remains within the mask cylinder circuit.

[Object of the invention] The object of the invention is to improve the brake pressure change in the front wheel brake, especially during brake pressure reduction, without requiring any additional components, i.e. to achieve an ideal brake pressure change. On the other hand, the objective is to make the brake pressure changes in the front wheel brakes more consistent. Furthermore, with regard to the operation when a pressure failure occurs in the front wheel brake circuit, it is desired that the operation be controlled in a desired operation mode according to each embodiment and any special requirements.

This objective is achieved by improving a brake system of the type described above, in which two independent hydraulic brake circuits are installed between the brake pressure generator and the front wheel brake. They are interconnected by a hydraulically actuated control element which almost completely compensates for the pressure difference in the brake pressure at the wheel brakes on the two front wheels.

According to the invention, by using one simple additional element, equal brake pressure is applied to both front wheel brakes during all brake applications, i.e. during normal braking and during brake slip control. It means that it can be transmitted. It is also possible to deliver the brake pressure completely, which is of primary importance in the case of small friction stops or small braking force coefficients.

Here, a brake pressure generator can be used in brake systems in which it is not possible to fully deliver the brake pressure of both brake circuits by actuation of a valve that reduces the boost. For example, a brake pressure generator It is applicable when the brake pressure generator is constructed as follows: the brake pressure generator consists of an open-center brake booster combined with a single-type mask cylinder and is equipped with a throttle valve. One of the two brake circuits is directly connected to this throttle valve, while a pressure fluid pump is provided as an auxiliary energy source.The discharge side of this pressure fluid pump is temporarily supplied with pressure via the valve. It can be connected to a supply reservoir 1, and this valve can be switched into the open position in order to reduce the boost effect, ie to reduce the auxiliary force transmitted to the brake force generator.

According to a preferred embodiment of the invention, the control element is constructed as a piston which is slidably arranged in the cylinder, with the end faces of the piston providing two
The chambers are defined and these chambers are connected to one of the two brake circuits.
are connected to each other.

Furthermore, in one embodiment of the invention, the piston of the control element is mechanically coupled with an isolation valve interposed in the pressure fluid path of the mask cylinder circuit between the brake pressure generator and the control element. be able to. This isolation valve is opened when the pressures are balanced or when the pressure in the second brake circuit connected to the throttle valve is high.

In particular, in the event of a pressure failure in the two brake circuits on the front wheel side, several additional switching elements can be inserted in the brake circuits and these Various variants are conceivable for generating the control values for the components.1 [Embodiment of the invention] FIG. 1 shows a particularly simple hydraulic braking system, which is distributed between a front axle and a rear axle. In addition to being able to control the braking force required to prevent the wheels from locking, it is also possible to reduce brake slippage by 11 to avoid wheel locking. Here, the hydraulic brake system has two brake circuits 1 and 2.
The brake circuits 1 and 2 are diagonally connected to two wheel brakes, respectively. The brake circuit 1 operates directly on the left front wheel brake 12 by means of a normally open separation valve (1X), which will be described later.
It acts on the wheel brake 15 for the right rear wheel through. The brake circuit 2 is directly connected to a wheel brake 13 for the right front wheel, and is also connected via a brake pressure regulator 7 to a wheel brake 14 for the left rear wheel.

These two brake circuits 1.2 are supplied with hydraulic pressure from a schematically illustrated hydraulic brake pressure generator 3. This brake pressure generator 3 is composed of a brake booster 4 and a single type mask cylinder 5. The pedal force applied to the brake pressure generator 3 is indicated by F in FIG.

The brake booster 4 is preferably an open center type booster in which a brake circuit is connected to a throttle valve (not shown) by known means.

The auxiliary energy source comprises a pressure fluid pump 8 , which is mechanically coupled to an electric motor 9 .

The discharge side of the pressure fluid pump 8 is connected to the brake booster 4, and the suction side of the pressure fluid pump 8 is connected to the reservoir 1.
1 (X).

A relief valve 10 is arranged to bypass the pressure fluid pump 8, and this relief valve 10 regulates the pressure of the pressure fluid sent out from the pressure fluid pump 8.

Further, wheel brakes 14 and 1 for left and right rear wheels are provided.
5 is connected to the reservoir 11 via check valves 16 and 17 which are hydraulically isolated from the rear wheel brake circuit and a two-bottom, two-position on-off valve 18 which is normally in the closed position.

Therefore, as will be described later, the pressure in the left and right rear wheel brakes 14 and 15 can be reduced through this pressure reduction system.

In the auxiliary energy supply circuit, brake booster 4
2-point, 2-position on-off valve 1 in parallel with the inlet and outlet of
9 is connected. One of the on-off valves is in a closed position when inactive. The on-off valve 19 has a boost effect, that is, a function to reduce the auxiliary energy transmitted to the brake pressure generator 3, thereby reducing the brake pressure in the left and right wheel brakes 12 and 13. can.

The separating valve 21 and the connected controller 20 are connected to two hydraulically independent brake circuits 1.2. The controller 20 has a cylinder 22 in which a piston 23 is slidably housed. The interior of the cylinder 22 is divided into two chambers 2 by both end surfaces of the piston 23.
4.25, and these chambers 24.25 are connected to the brake circuits 1 and 2, respectively. The above separation valve 21
is inserted in the pressure line between the mask cylinder 5 and the controller 20 in the brake circuit 1.

This isolation valve 21 is open as long as the pressures in the chambers 24, 25 are balanced or the pressure in the chambers 25 is higher than in the chamber 24.

In order to determine the rotational state of the wheels, all wheels are equipped with sensors S1 to S4, which transmit the rotational state of the wheels in the form of electrical signals to an electronic evaluation circuit 2.
6. In this electronic evaluation circuit 26, control signals are generated for controlling the brake pressure regulator 6.7 and the on-off valve 18.19. Here, these brake pressure regulators 6.7 and on-off valves 18.19 are electromagnetically operated two-point/two-position switching valves, and these brake pressure regulators 6.7 and on-off valves 18.19 is in the closed position in its initial position, ie in the demagnetized state.

Next, the operation of the hydraulic brake system shown in FIG. 1 will be explained.

By applying a pressing force F to the brake pedal,
When the brakes are applied, the pressure within the two brake circuits 1 and 2 is immediately raised in response to this pedal force F.
The pressure is then increased by the auxiliary hydraulic energy generated by the pressure fluid pump 8. By throttling the pressure fluid sent from the pressure saw fluid pump 8 at a throttle (not shown) in the brake booster 4, hydraulic pressure that directly acts on the brake circuit 2 is raised, and this hydraulic pressure is applied to the piston in the mask cylinder 5. increase the force acting on

However, only after the two brake pressure regulators 6, 7 have been activated or switched, the hydraulic pressure is transferred to the pressure line 2 leading to the wheel brakes 14 and 15 for the left and right wheels.
7.28. By appropriately setting the electronic evaluation circuit 26, the brake pressure at the left and right rear wheel brakes 14 and 15 follows the brake pressure at the left and right front wheel brakes 12 and 13 with a delay; It is supplied depending on the wheel slip value determined with the help of sensors S1 to $4. In this configuration, the rear wheel slip value is less than or at most equal to the front wheel slip value.

When a front wheel or rear wheel is about to become locked, brake slip control is initiated. To prevent further build-up of the brake pressure at the rear axle, it is sufficient to switch the brake pressure regulator 6.7 back into the closed position. If it is necessary to reduce the brake pressure at the rear axle, the on-off valve 18 is energized, so that the brake pressure at the rear axle is released into the reservoir 11 via the check valve 16, 17, and The pressure is reduced to the desired low pressure level by an electronic evaluation circuit that controls the switching time of the on-off valve 18.

To reduce the brake pressure at the front axle, the on-off valve 19 is energized. This causes the inlet and outlet of the auxiliary energy port in the brake pressure generator 3 to be short-circuited. In other words, the hydraulic pressure in the brake circuit connected to the brake booster 4 is completely reduced, and the hydraulic pressure in the brake circuit 2 connected to the mask cylinder 5 is proportional to the depression force F of the brake pedal. The pressure is reduced to the residual liquid pressure. The resulting controller 20
Due to the unbalance of hydraulic pressure within
3 is moved to the right and as a result the isolation valve 21 is closed. As a result, the mask cylinder 5 is separated from the left front wheel brake 12, and it becomes possible to similarly reduce the pressure of the pressure saw inside the mask cylinder 5 to below the residual hydraulic pressure.

Another advantage of the controller 20 in combination with the isolation valve 21 is that the reduction in brake pressure at the front wheels is not transmitted to the piston of the mask cylinder. This prevents brake pedal vibration.

Even if the brake circuit 1 fails, the brake circuit 2 is maintained fully operable.

In order to ensure pressure transmission to the left-hand front wheel brake 12 even if the brake circuit 2 fails, in the embodiment of FIG. is being done.

A check valve 30 is connected in parallel to the switching valve 29. In the inactive position, ie as long as there is no control pressure at ports P1 and P2, the hydraulic boat is closed by the switching valve 29. The control pressure for operating the switching valve 29 is provided by a throttle 31 inserted in the auxiliary energy supply circuit.
or generated by 32. A throttle 31 arranged in the main delivery line of the pressure fluid pump 8 controls the control force Pi, P2 of the switching valve 29 at each brake activation, that is, whenever the pressure fluid pump 8 is delivering pressure fluid. A signal depending on the pressure difference Δp is output, and this causes the switching valve 2 to
9 to the closed position. If the pressure fluid pump 8 does not deliver pressure fluid, ie no pressure fluid is delivered via the throttle 31, then the actuation of the controller 20 is blocked. This is because when the switching valve 29 is closed, the piston 23 cannot move. As a result, the separation valve 21 remains open. Therefore, when the supply of auxiliary energy fails, the left front wheel brake 1 is transferred from the mask cylinder 5 through the brake circuit 5.
The pressure line leading to 2 is kept open.

The pressure line via the non-return valve 30 will in any case bring the piston 23 of the controller 20 into its initial position, in which the isolation valve 21 is open, when the brake pedal is returned.
guarantees that it can be slid back into place.

Instead of the throttle 31, the throttle 32 can likewise be used to generate the control pressure difference Δp' according to FIG. During brake slip control, even if the on-off valve 19 is energized because the brake pressure transmitted to the front wheels is too high, the control pressure difference Δ that causes the switching valve 29 to switch
p' occurs only in the aperture 31. If the auxiliary energy supply or brake circuit 2 fails, no control pressure can be generated at the throttle 32 either.

Instead of the switching valve 29 in FIG. 2, a hydraulically operated switching valve 33
can be similarly inserted into the brake circuit 1 connecting the mask cylinder 5 and the left front wheel brake 12. However, the switching valve 33 must be switched to the open position when inactive, ie, when there is no control pressure. This embodiment is shown in FIG. In this embodiment, the switching valve 33 includes a separation valve 21 and a controller 20;
It is arranged in parallel to the pressure passage connecting the left front wheel cylinder 12 and the mask cylinder 5.

As in the embodiment of FIG.
Alternatively, it can be obtained by using a throttle connected in series with one on-off valve that short-circuits the auxiliary energy circuit.

FIG. 4 shows another embodiment in which interruption of the brake circuit 1 can be avoided in the event of a failure of the brake circuit 2 or the auxiliary energy circuit. In this embodiment, a controller 34 co-located with controller 20 and mechanically coupled to isolation valve 21 includes a spring-loaded catch 35 that As long as the dynamic pressure P generated by the piston 3 of the controller 34 is smaller than the value determined by the biasing spring 37 of the catch 35,
6 is held in its initial position. Therefore, the functionality of the controller 34 is always ensured when the pressure fluid pump 8 is operating normally. If the auxiliary energy circuit fails, no dynamic pressure will be created in the throttle 31 and the catch 35 will prevent any movement of the screws 36.

In the embodiment shown in FIG. 5, the brake circuit 2 is connected to the chamber 25 of the controller 20, opposite the isolation valve 21, via a switching member 38, which is shown as a hydraulically actuated slider. ing. The switching member 38 is substantially a cylinder;
It consists of a piston 39 slidably housed within this cylinder.

This switching member 38 allows the pressure fluid delivered from the pressure fluid pump 8 to flow through the ports C, D and as shown by the arrows, and functions like a two-point 1-2 position switching valve.

- In the inactive position, the flow from the inlet A of the switching element 38 to the outlet B, ie to the chamber 25 of the controller 20, is blocked. When pressure fluid is delivered from the pressure fluid pump 8, the dynamic pressure generated at the restriction of the piston 39 is applied to the reset spring 4.
The piston 39 is moved against the biasing force of the brake circuit 2 and the controller 20! Open a passage connecting 25. Furthermore, its mode of functioning can be compared with that of the embodiment of FIG.

Finally, the invention may also be the embodiment of FIG. In this embodiment, a check valve 40 capable of intermittent hydraulic operation is interposed between the hydraulic port of the controller 20 and the wheel brake 13 for the right front wheel, that is, the brake circuit 2. This check valve 40 will not open the pressure fluid passage until the pressure in the brake circuit 2 has risen above a predetermined minimum pressure, for example 1 bar. In the event of a failure of the brake circuit 2, for example the auxiliary energy circuit, the check valve 14 is closed, thereby locking the piston 23 of the controller 20. As a result, the separation valve 21 in the brake circuit 1 is kept open. This means that the connection between the left front wheel brake 12 and the mask cylinder 5 is maintained, and even if the boost force from the brake booster does not work and the auxiliary energy circuit fails, the left front wheel can be braked. It means.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a hydraulic brake system showing one embodiment of the invention, and FIGS. N2 to 6 are circuit diagrams of hydraulic brake systems showing further embodiments of the invention. 1.2... Brake circuit, 3... Brake pressure generator, 4... Brake booster, 5... Mask cylinder, 6°7... Brake pressure regulator, 8... Pressure fluid pump , 11...Reservoir, 12.13...Front wheel brake, 14.15...Rear wheel brake, 16°17.30.40...Check valve, 18.19.
...Opening/closing valve, 21.29.33...Switching valve, 20.3
4... Controller, 22... Cylinder, 2.3, 36.
39...Piston, 24.25...Empty, 26...
Electronic evaluation circuit, 35...Catch, 38...Switching member Fig, 1

Claims (15)

[Claims] (1) A dual brake circuit connected to the front and rear wheel brakes, a pedal-operated brake pressure generator consisting of a brake booster and a mask cylinder, connected to an auxiliary energy source, and a rear brake circuit connected to the front and rear wheel brakes. A brake pressure regulator arranged in a pressure passage leading to the wheel brake, a pressure fluid passage leading from the wheel brake of the rear wheel to a pressure fluid reservoir, and an isolation valve adapted to be switched into the open position. a switching valve that reduces the boost effect by reducing the auxiliary energy transmitted to the brake pressure generator; a switching valve that determines and evaluates the rotational state of the wheels and influences the brake pressure changes of the front and rear wheels; When a tendency to lock appears in the wheel, it does not affect the change in brake pressure. A hydraulically actuated controller is interconnected between the generator and the front wheel brake, the controller being characterized in that the controller compensates for brake compression in the first and second brake circuits. brake system. (2) The operation of the switching valve that reduces the boost effect completely reduces the brake pressure in one of the first and second brake circuits connected to the brake pressure generator, and reduces the brake pressure in the other brake circuit to the brake pedal force. Hydraulic brake system according to claim 1, characterized in that the brake pressure is reduced to a dependent pedal pressure. (3) The brake pressure regulator is configured as an open center brake booster including a single type mask cylinder, and the brake pressure regulator is directly connected to the other of the first and second brake circuits. a pressure fluid pump is provided as the auxiliary energy source, the discharge side of the pressure fluid pump is connected to the reservoir via a switching valve, and the switching valve is switched to an open position. Hydraulic brake system according to claim 2, characterized in that it is adapted to be actuated. (4) The controller has screws i~ that are slidable inside the cylinder.
Claim 1, characterized in that each chamber in the cylinder defined by both end surfaces of the piston is connected to the first and second brake circuits, respectively. The hydraulic brake system according to any one of items 3 to 3. (5) The piston of the controller is mechanically coupled to an isolation valve, the isolation valve being in a pressure fluid path of one of the first and second brake circuits between the brake pressure generator and the controller. The isolation valve is inserted when similar brake pressures are present in the first and second brake circuits and in the pressure fluid line connecting the other brake circuit, i.e. the brake pressure generator, and the front wheel brake. Hydraulic brake system according to claim 4, characterized in that it is opened when the transmitted brake pressure is high. (6) The brake pressure regulator consists of an oven center type brake booster and a single type mask cylinder, and the separation valve is inserted into the first brake circuit on the front wheel side connected to the mask cylinder. The hydraulic brake system according to claim 4, characterized in that: (7) The second brake circuit on the front wheel side connected to the brake booster opens a hydraulically operated switching valve and is connected to the controller, and this switching valve is closed in the non-operating position and the auxiliary brake circuit is connected to the controller. The switching valve is configured to be in an open position when a control pressure transmitted from the energy circuit is applied, and a check valve that opens toward the controller is connected in parallel to the switching valve. A hydraulic brake system according to claim 5. (8) In the first brake circuit on the front wheel side connected to the mask cylinder between the brake pressure generator and the front wheel brake, a hydraulically operated switching valve is inserted in parallel with the separation valve and the controller. 7. The hydraulic brake system according to claim 6, wherein the switching valve is in an open position in a non-actuated state and is in a closed position when a control pressure is applied. (9) The control pressure controlling the switching valve between the brake pressure generator and the front wheel brake can be derived from the pressure difference obtained by a throttle inserted in the auxiliary energy circuit. A hydraulic brake system according to claim 7 or 8, characterized in that: (10) In order to generate control pressure to switch the switching valve inserted in the pressure fluid path between the brake pressure generator and the front wheel brake, the discharge side of the pressure fluid pump and the brake pressure generator are connected. 10. The hydraulic brake system according to claim 9, further comprising a throttle connected in series therebetween. (11) A restriction is placed on the switching valve to temporarily connect it to the auxiliary energy source in order to generate the control pressure to switch the switching valve, and to short-circuit the connection to the auxiliary energy source to reduce the boost effect. Hydraulic brake system according to claim 9, characterized in that the hydraulic brake system is connected in series. (12) The piston of the controller is hydraulically actuated, and the isolation valve coupled to the piston is switched to the open position and locked in the initial position by a catch biased by a spring. 7. The hydraulic brake system according to claim 6, wherein the catch is disengaged from the piston by control pressure. (13) The control pressure for disengaging said catch is derived from the pressure difference generated by a restriction arranged in the auxiliary energy circuit between the discharge side of the pressure fluid pump and the brake pressure generator. 13. A hydraulic brake system according to claim 12. (14) The second brake circuit connected to the brake booster is connected to the controller via a piston/cylinder unit, and the piston/cylinder units 1~ are arranged in the pressure fluid conduit of the pressure fluid pump of the auxiliary energy source. The piston of the piston-cylinder unit is in its initial position, i.e. as long as the pressure fluid pump is not delivering pressure fluid, from the wheel brake to the controller. and the piston is movable by the flow of pressure fluid against the biasing force of a reset spring, thereby opening a passage from the wheel brake to the controller. A hydraulic brake system according to claim 6. (15) The second brake circuit for the front wheels connected to the brake booster is connected to the controller via a hydraulically operated check valve, and the check valve is connected to the second brake circuit for the front wheels connected to the brake booster. Hydraulic brake system according to claim 6, characterized in that it is opened when the pressure within exceeds a predetermined threshold.